Transparent cutting oil



United States Patent 2,918,432 Patented Dec. 22, 1959 ice TRANSPARENT CUTTING OIL I-Ming Feng, Detroit, Mich., assignor to Ethyl Corporation, New York, N.Y., a corporation of Delaware N Drawing. Application May 29, 1957 Serial No. 662,329

3 Claims. (Cl. 252--46.7)

This invention relates to transparent cutting oil having superior performance characteristics by virtue of the presence therein of a highly effective additive.

In metal cutting the material that is detached from the work piece forms the chip which moves in sliding contact up the face of the cutting tool. The rubbing between the chip and the tool face represents a condition of ineffective boundary lubrication. In order to avoid the serious consequences of this ineffective lubrication, various cutting oil additives have been proposed and developed. These additives improve the lubrication properties of the oil. Almost without exception those cutting oils having any significant effectiveness have been so highly fortified with various additives that they are opaque. Thus, in use these cutting oils have involved a sacrifice in visual observation of the work. In some cases, transparent cutting oils of reasonably good performance quality have been developed, but these have been unsatisfactory because they require the use of highly expensive additive complements.

The problem of developing an effective cutting oil is further complicated by the fact that there does not appear to be any satisfactory correlation between the physical properties of cutting fluids and their cutting performance. For example, Ernst and Merchant (Chip Formation, Friction and Finish, The Cincinnati Milling Machine Company, Cincinnati, Ohio (1940)) tried without success to correlate cutting performance with cutting oil physical properties, such as absolute viscosity, boiling point, surface tension, specific heat, dielectric constant, electric moment and density. Thus, the development of effective cutting oils and additives is largely an empirical art;

It is seen that the need exists for an inexpensive transparent cutting oil having excellent performance characteristics under actual cutting operations.

An object of this invention is to fulfill the foregoing need. Another object is to provide transparent cutting oil having superior performance characteristics. A further object is to provide highly effective additives for use in cutting oil. A still further object is to provide improved methods of carrying out metal cutting operations. Other important objects will be apparent from the ensuing description.

The above and other objects of this invention are accomplished by providing a transparent cutting oil consisting essentially of a transparent lubricating oil and from about 0.5 to about 15 percent by weight of a monochlorophenyl dimethyl phosphorothionate. The phosphorus additive has been shown in actual cutting operations to impart greatly superior performance characteristics to the base oil. Furthermore, the phosphorus additive is a water-white liquid and thus enables the provision of transparent cutting oils. The phosphorus additives are easily made from inexpensive starting materials and thus provide the foregoing technical benefits at low cost.

The base oil used in the compositions of this invention is preferably water-white to amber in color, although oils with somewhat darker coloration (tan to brown) can be successfully used. The chief transparency characteristics of the base oil is that it not be so dark as to be opaque even when spread over a surface as a film. The base oil is preferably a mineral lubricating oil because these are readily available at low cost and have good solvent and lubricating properties. However, various synthetic lubricating oils can be successfully used in the compositions of this invention. Of the mineral lubricating oils, naphthenic oils are particularly preferred because they are less costly than comparable paraffinic oils and, in general, have a higher solubility for the phosphorothionates than do the other mineral base oils. Nevertheless, very good results are achieved by using parafiinic and mixed base mineral oils. Suitable synthetic oils for use in this invention include olefin polymer oils (polybutenes, polymerized paraffin wax olefins, etc), polyalkylene glycol oils, silicone oils, diester oils (sebacates, adipates, etc.), chlordiphenyl oils, and the like.

The base oils should have a viscosity of F. of from about 50 to about 500 Saybolt Universal seconds (SUS), although variations from these values are permissible depending in part upon the use to which the cutting oil is to be put. For example, it is generally desirable to use less viscous base oils in formulating cutting oils to be used in high-speed, continuous machinery operations. For most cutting operations, it is preferable that the base oil have a viscosity of from about 100 to about 250 SUS at 100 F.

The phosphorothionate used to fortify the above base oils is a monochlorophenyl dimethyl phosphorothionate having the general formula 01 S OCH;

OCH:

Besides being substituted by a chlorine atom, the phenyl group can also be substituted with one or more methyl and/or ethyl groups. It is preferable that the total number of carbon atoms in such methyl and/or ethyl groups present in the phenyl nucleus be no greater than five. The purpose of these methyl and/ or ethyl substituents is primarily to improve the solubility of the phosphorothionate in some of these base oils. Apart from this feature, the presence or absence of such alkyl groups in the phenyl group has no apparent effect upon the ability of the phosphorothionate to exert its outstanding effectiveness. In short, the tremendous effectiveness as cutting oil additives of the monochlorophenyl dimethyl phosphorothionates is tied in in some unexplainable manner with the fundamental molecular configuration of the compound. Thus, the combination of a phosphorus atom, a coordinate covalent bonded sulfur atom, a monochlorophenyl ester group and two methyl ester groups results in an inter-play of factors which directly leads to the tremendous effectiveness of the additives.

In formulating the improved cutting oils of this invention an appropriate concentration of the phosphorothionate is blended with a suitable base oil. To insure homogeneity, physical agitation is helpful. If desired, concentrated solutions in the range of 50 percent by weight or more of the phosphorothionate can first be formed and these, in turn, be diluted with additional oil to the desired concentration.

The outstanding effectiveness of the cutting oils of this invention was demonstrated by a series of metal cutting tests. The tests were carried out on a milling machine with a highspeed steel tool (rake angle: 15; clearance angle: 5). The steel of this tool containing 18 percent of tungsten, 4 percent of chromium, and 1 percent of vanadium is known in the art as an l8-41 steel. The Work material was SAE 1018 steel. The length of the specimen in the direction of the cut was two inches and its width in the direction parallel to the cutting edge was 0.25 inch. A constant depth of cut of 0.015 inch and a cutting speed of 12.25 inches per minute were used in all tests.

A newly-ground tool-tip was used for each test. The chip that was formed during the first cut was discarded to eliminate the efi ect of any contamination originally on the tool surface, and to allow conditions to reach an equilibrium state. Whenever backing of the too] to the starting point was necessary, the tool was raised to prevent it from dragging over the surface.

Two criteria of effectiveness were used. The first was the chip length since it is well known in the art that the chip length is directly proportional to the effectiveness of the boundary lubrication, hence, to the effectiveness of the cutting oil. The second criterion was the quality of the surface finish as determined by visual inspection upon completion of the cutting operation.

A typical cutting oil of this invention, made from a mineral oil having an SUS viscosity at 100 F. of 100 containing percent by weight of p-chlorophenyl dimethyl phosphorothionate was subjected to the above test. An identical test was carried out using the above base oil in the absence of any additive. it was found that the chip length resulting from the use of the cutting oil of this invention was 1.00 inch, whereas the unfortified base oil gave a chip length of only 0.73 inch. it was also noted that the surface finish resulting from the use of the cutting oil of this invention was far superior to that achieved when employing the additive-free base oil.

To still further appreciate the outstanding effectiveness of the cutting oils of this invention, many identical tests were carried out using commercially available cutting oils from various suppliers. In all, seven such commercial cutting oils were subjected to the same test conditions, all of these oils being highly fortified with additives to the extent that they were pitch black in color. It was found that the cutting oil of this invention was more effective than even the best of these seven commercial cutting oils. It is thus clear that this invention represents a decided advance in the art.

Typical cutting oils of this invention are illustrated by the following specific examples in which all percentages are by weight.

Example 1 Pennsylvania neutral mineral oil (185 SUS at 100 F.) containing 0.5 percent of p-chlorophenyl dimethyl phosphorothionate.

Example II Mid-Continent neutral mineral oil (290 SUS at 100 F.) containing 3 percent of o-chlorophenyl dimethyl phosphorothionate.

Example III California neutral mineral oil (382 SUS at 100 F.) containing 5 percent of m-chlorophenyl dimethyl phosphorothionate.

Example IV Solvent-extracted paraflinic mineral oil (155 SUS at 100 F.) containing 1 percent of an equimolar mixture of o-chlorophenyl dimethyl phosphorothionate and pchlorophenyl dimethyl phosphorothionate.

Example V Coastal neutral solvent-extracted mineral oil (311 SUS at 100 F.) containing 2 percent of p-chloro-m-tolyl dimethyl phosphorothionate.

Example VI Solvent-extracted Pennsylvania bright stock (500 SUS at 100 F.) containing 7 percent of 4-chloro-3,5-dimethylphenyl dimethyl phosphorothionate.

4 Example VII Conventionally-refined Pennsylvania neutral mineral oil (99 SUS at 100 F.) containing 15 percent of 5-chloro- 2,4-diethylphenyl dimethyl phosphorothionate.

Example VIII Conventionally-refined Coastal oil (440 SUS at 100 F.) containing 10 percent of 3-chloro-2,4,6-trimethylphenyl dimethyl phosphorothionate.

Example IX Polybutene oil (537 SUS at 100 F.) containing 1.5 percent of 4-chloro-2-methyl-6-ethylphenyl dimethyl phosphorothionate.

Example X Polybutene oil (114 SUS at 100 F.) containing 4 percent of 3-chloro-4-methyl-2,6-diethylphenyl dimethyl phosphorothionate.

Example XI Polymerized trimethylethylene (367 SUS at 100 F.) containing 3 percent of p-chlorophenyl dimethyl phosphorothionate.

Example XII Polyalkylene glycol SUS at 100 F.) containing 12 percent of 4-chloro-2,5,6-trimethylphenyl dimethyl phosphorothionate.

Example XIII Polyalkylene glycol (525 SUS at 100 F.) containing 6 percent of o-chlorophenyl dimethyl phosphorothionate.

Example XIV Silicone polymer oil (polymethyl siloxane) having an SUS viscosity at 100 F. of containing 0.75 percent of 2-chloro-3,5 -diethylphenyl dimethyl phosphorothionate.

Example XV Di-(sec-amyl) sebacate (50 SUS at 100 F.) contain ing 15 percent of an equimolar mixture of o-chlorophenyl dimethyl phosphorothionate and p-chlorophenyl dimethyl phosphorothionate.

Example XVI Di-(Z-ethylhexyl) sebacate (68 SUS at 100 F.) containing 5 percent of monochlorotolyl dimethyl phosphorothionate (mixed isomers).

Example X VII Di-(Z-ethylhexyl) adipate (53 SUS at 100 F.) containing 3 percent of monochloroxylyl dimethyl phosphorothionate (mixed isomers).

Example XVIII Chlor-diphenyl oil (90 SUS at 100 F.) containing 1 percent of 4-chloro-2,3,5,6tetramethylpheuyl dimethyl phosphorothionate.

The above cutting oils all have superior cutting oil characteristics by virtue of the presence therein of the phosphorothionates. Moreover, they have the distinct advantage of being transparent thereby permitting visual observation of the cutting work. Other cutting oils of this invention will now be apparent to one skilled in the art.

The cutting oils of this invention can contain other additives, such as dispersants, antioxidants (alkyl phenols, etc.), and the like.

The preparation of the above and other phosphorothionates used according to this invention involves procedures known in the art. One useful process is described in US. Patent 2,784,207.

The cutting oils of this invention can be used in the form of so-called soluble oils. This involves blending with one of the finished lubricants of this invention a small amount of a conventional dispersing agente.g., sul-,

fonates, sulfonated fatty oils, etc.and emulsifying this mixture with water. The methods of formulating soluble oils are well known to those skilled in the art. Generally speaking, the degree of dilution of a soluble oil with water is varied from 1:5 to 1:100 (parts by volume respec tively). These water-soluble oils or oil-water emulsions are particularly useful for certain high-speed cutting operations.

I claim:

1. A transparent cutting oil consisting essentially of a transparent lubricating oil and from about 0.5 to about 15 percent by weight of a monochlorophenyl dimethyl phosphorothionate having the formula Cl S 00113 OCH:

3. The composition of claim 2 wherein said phosphorothionate is p-chlorophenyl dimethyl phosphorothionate.

References Cited in the file of this patent UNITED STATES PATENTS 2,542,604 Weisel \Feb. 20, 1951 

1. A TRANSPARENT CUTTING OIL CONSISTING ESSENTIALLY OF A TRANSPARENT LUBRICATING OIL AND FROM ABOUT 0.5 TO ABOUT 15 PERCENT BY WEIGHT OF A MONOCHLOROPHENYL DIMETHYL PHOSPHOROTHIONATE HAVING THE FORMULA 